This invention relates to a reversible auto document feeder for use in image forming apparatus, such as copying machines and facsimile terminals, which makes it possible to reverse a document.
Image forming apparatus carrying an auto document feeder have been widely used more and more. Recently there has also been provided a reversible auto document feeder which, in addition to the conventional function of feeding a document automatically, makes it possible to automatically reverse a document so as to copy images on its both sides by a simple operation.
The above-mentioned reversible auto document feeder is so designed that it operates in response to signals from a main body of an image forming apparatus. Specifically, when the reversible auto document feeder receives a signal for auto document feeding (referred to as ADF hereinafter) from the main body, it feeds a document to a document placing position and then discharges the document after copying. When the reversible auto document feeder receives a signal for reversible auto document feeding (referred to as RADF hereinafter) from the main body, it feeds a document to the document placing position, then reverses the document, feeding the document to the document placing position again, and finally discharging it. In this way, the operation of a conventional reversible auto document feeder is unilaterally determined by signals from a main body of an image forming apparatus. In other words, it is determined by signals from the main body which of ADF and RADF the feeder executes.
In image forming apparatus which are currently available, there is one having a function of forming images on both sides of copying paper (hereinafter referred to as a double-side machine) and another not having such a function (hereinafter referred to as a single-side machine). The double-side machine is constructed so as to send both ADF and RADF signals. Accordingly, the double-side machine which is equipped with a reversible auto document feeder can perform the following functions:
(1) Forming images of a double-sided document on both sides of copying paper PA0 (2) Forming images of a double-sided document on one side of copying paper PA0 (3) Forming an image of a single-sided document on both sides of copying paper PA0 (4) Forming an image of a single-sided document on one side of copying paper
Also, it will be theoretically seen that the single-side machine which is equipped with a reversible auto document feeder can perform (2) and (4) of the above-mentioned functions.
However, the single-side machine sends only an ADF signal. On the other hand, with a conventional reversible auto document feeder, its operation is determined by a signal from the main body of the image forming apparatus as described above. Consequently, even if such a conventional reversible auto document feeder is attached to the single-side machine, only function (4) can be performed. Thus, conventional reversible auto document feeders have not fully performed its function.
An auto document feeder capable of reversible auto document feeding is found in Japanese Unexamined Patent Publication No. 62-180829. It should be noted that a reversible auto document feeder of the above invention is applied only for image forming apparatus, whose main body sends a RADF signal.